The subject matter disclosed herein relates to an ultrasonic flow measurement system.
Flow meters, including ultrasonic flow sensors, are used to determine the characteristics (e.g., flow rate, pressure, temperature, etc.) of liquids, gases, etc. flowing in pipes of different sizes and shapes. Knowledge of these characteristics of the fluid can enable other physical properties or qualities of the fluid to be determined. For example, in some fluid custody-transfer applications, the flow rate of the fluid can be used to determine the volume of a fluid (e.g., oil or gas) being transferred from a seller to a buyer through a pipe over a period of time to determine the costs for the transaction/The volume is equal to the measured fluid flow rate multiplied by the cross sectional area of the pipe multiplied by the period of time over which the fluid flow is measured.
In one type of ultrasonic flow sensor employing transit time flow metering, one or more pairs of ultrasonic flow sensors can be installed along a portion of a pipe, referred to as a flow cell. Each pair of ultrasonic flow sensors contain an ultrasonic transducer and an ultrasonic buffer that are located upstream and downstream from each other, forming an ultrasonic path between these ultrasonic flow sensors at particular chordal locations across the pipe.
Each transducer, when energized, transmits an ultrasonic signal (e.g., a sound wave) along an ultrasonic path through the flowing fluid that is received by and detected by the other transducer. The path velocity of the fluid averaged along the ultrasonic path at a particular chordal location can be determined as a function of the differential between (1) the transit time of an ultrasonic signal traveling along the ultrasonic path from the downstream transducer upstream to the upstream transducer against the fluid flow direction, and (2) the transit time of an ultrasonic signal traveling along the ultrasonic path from the upstream transducer downstream to the downstream transducer with the fluid flow direction. Ultrasonic flow meters use signal processing techniques to identify the ultrasonic signals received by the transducers and the time that those ultrasonic signals were received in order to determine the transit times used to determine the flow rate of the fluid.
In some ultrasonic flow measurement systems (e.g., ultrasonic signals of a few megahertz or less where the wavelength of the ultrasonic signal is not significantly less than the diameter of the ultrasonic buffers), the spreading of the ultrasonic signal beam as it propagates within the ultrasonic buffer can result in distortion in the form of multiple ring-down signals and peaks in the received ultrasonic signal. This distortion is a result of angular portions of the ultrasonic signal reflecting off of the walls of the ultrasonic buffer. When these ring-down signals and peaks resulting from the distortion have amplitudes that are comparable or greater than the amplitudes of the main (non-angular) portion of the ultrasonic signal, the signal processing of the ultrasonic flow meter may not be able to accurately identify the main portion of the ultrasonic signal from which the transit time is determined.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.